Endogenous opioid peptides have been shown both in animals and in man to have profound and long lasting analgesic effects when injected in the cerebrospinal fluid. A limited number of techniques are available for relieving pain in patients with chronic pain and are not always successful. The present study is designed to confirm the finding that beta endorphin injected intrathecally in man is a powerful analgesic agent and to evaluate the neurophysiological, metabolic, systemic and behavioral actions of such an injection. It is carried out on patients with advanced disseminated cancer and intractable pain which is beyond conventional methods of relief. Double blind injection of drug or placebo is done four days apart and the same clinical assessment is carried out after both injections. In case of lack of pain relief, systemic conventional pain relief is immediately resumed. The whole protocol is carried out under close medical and nursing supervision during its entire duration in order to keep inconveniences and hazards to the patient to a minimum.